linux-kernel - Re: Make RCU dcache work with CONFIG

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Message-ID: <20110422211649.GW16484@one.firstfloor.org>
Date:	Fri, 22 Apr 2011 23:16:49 +0200
From:	Andi Kleen <andi@...stfloor.org>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Andi Kleen <andi@...stfloor.org>, linux-fsdevel@...r.kernel.org,
	akpm@...ux-foundation.org, linux-kernel@...r.kernel.org,
	npiggin@...nel.dk, shaohua.li@...el.com, sds@...ho.nsa.gov,
	jmorris@...ei.org, linux-security-module@...r.kernel.org,
	Eric Paris <eparis@...isplace.org>
Subject: Re: Make RCU dcache work with CONFIG_SECURITY=y

On Fri, Apr 22, 2011 at 11:26:09AM -0700, Linus Torvalds wrote:
> On Thu, Apr 21, 2011 at 5:23 PM, Andi Kleen <andi@...stfloor.org> wrote:
> >
> > I didn't find good test suites for the security modules, so
> > there wasn't a lot of testing on this unfortunately
> > (the selinux one for LTP doesn't seem to work). Some close
> > review of these changes is needed.
> >
> > On the other hand the VFS changes itself are very straight forward
> > and the 1/1 patch is very straight forward (and a win in itself)
> >
> > The bottom line is with this patchkit a CONFIG_SECURITY=y
> > kernel has as good VFS performance as a kernel with CONFIG_SECURITY
> > disabled.
> 
> Gaah. My immediate reaction to the patch-series was "This is great, I
> was really hoping we could get all those annoying cases sorted out,
> and I'll queue them for the next merge window".
> 
> Having then actually read through the patches a bit more, I then got
> convinced that at least the first patch should probably be applied
> right away and be marked for stable, since it looks pretty damn
> obvious to me, and it might already on its own fix the performance
> regression for some configurations (although realistically I guess few
> enough people really do the "selinux=0" thing, so the big advantage is
> making easier to backport the other patches later if we don't do them
> now).

Yes I agree. The first patch is (nearly) a no-brainer and already
has significant benefits. I would like to see it in .39.

> Comments? I'd really like to see/hear feedback like "yeah, this looks
> really obviously safe" vs "yeah, looks good, but I really don't feel
> very comfortable with it" from the security people.

Especially SMACK review is needed. Or maybe selinux only for now,
already got one ack for that.

(BTW I have some doubts on the locking in smack in general, 
but that's a separate issue -- see other thread)

-Andi

-- 
ak@...ux.intel.com -- Speaking for myself only.
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